The present invention relates to an electronic connector and the packaging structure of a semiconductor device (LSI) for employing the same.
A pin connector includes a pin, a socket for receiving the pin, and a packaging portion, with the pin connector being extensively used as an electric or electronic connection component. With enhancement in a density of a computer, the importance of the connectors is being re-recognized as one of the packaging techniques, and a conventional pin connector includes a socket portion of a spring member, principally made of a Cu-Be alloy, with a pin to be inserted being connected by a spring force of the socket portion. The socket portion is arranged in parallel with a direction of insertion of the pin, and the pin is held between the springy parts of the spring member (or in the cylinder thereof). Recently, with enhancements in the packaging densities of electric and electronic components and the density of a computer, it has been necessary to compact and miniaturize the connectors. All of the conventional socket shapes pose a serious problem when attempting to compact and miniaturize the same, since the socket includes a cylindrical spring member and a certain height is needed in the pin inserting direction, with the wall of a socket package increasing in thickness. Additionally, since the socket shape is complicated, manufacturing is difficult in case of the miniaturization of the connector, and hence, the shape needs to be simplified. On the other hand, the enhanced density of a computer leads to increase in the number of pins of the connector and, since the number of pins to be inserted increases, a force for inserting the pins into the socket increases. With the large number of pins, the manufacturing of the connector, based on the spring force of the socket, becomes difficult. It has therefore been proposed to develop a low or zero insertion force connector in which pins can be inserted or drawn out by a small force while nevertheless ensuring a reliable connection in the joined state.
In, for example, Japanese Laid-Open Patent Application No. 57-185680, a connector is proposed wherein a hole is provided in the central part of a flat spring member, and a male contactor is inserted in the hole. One disadvantage of this proposed construction resides in the fact that it is very difficult to draw out the male contact.
In, for example, Japanese Laid-Open Patent Application No. 58-17572 or 58-73973, an electric connector for a Josephson element semiconductor device is proposed, which is operated at a very low temperature by the deformation of a bimetal with a temperature change. However, a disadvantage of these proposals resides in the fact that with an electric connector employing the bimetal only a relatively large bimetallic element can cause a sufficient deformation thereby making it difficult for the connector to be miniaturized.
An electric connector wherein the cylindrical socket is made of a shape memory alloy is proposed in `Kinzoku Binran (Handbook of Metals)` (fourth revised edition, December 1982); however, this proposed connector cannot be miniaturized.
An object of the present invention is to provide a connector in which male contacts can be inserted and drawn out with low forces, and the packaging structure of a semiconductor device employing the connector.
The present invention includes a connector comprising an insulating substrate having a plurality of through-holes and a desired first circuit pattern formed on the substrate. Female contacts are each formed and fixed around the edge of the through-hole and have an opening, with an edge thereof extending inwardly of the through-hole. The female contacts are electrically connected to the first pattern, and a male contact includes an insulating substrate having a desired second circuit pattern thereon, with a plurality of male contact pins being fixed to the substrate and electrically connected to the second pattern. The pins are each located in a position corresponding to each of the openings of the female contacts, and the female contacts are made of a thin film of a shape memory alloy and an edge of each of the female contacts is given, prior to insertion of each of the male contact pins, such a shape memory that the contact is returned to a position to close the opening when the contact is subjected to a temperature above the martensitic transition temperature.
Additionally, in accordance with the present invention, a part of a female contact forming a hole is provided with a slit so as to be adapted for a bending deformation due to an insertion of a male contact and has a shape memory so as to be adapted for the bending deformation in the same direction as that of the insertion of the male contact, whereupon the female contact is brought into contact with the male contact.
Generally known as shape memory alloys are a Cu alloy containing 0-10wt% of Al and 10-40wt% of Zn, a Cu alloy containing 23-26wt% of Sn, a Cu alloy containing 12-15wt% of Al and 3-5 wt% of Ni, an alloy consisting of 42-48wt% of Ti and a balance of Ni, and so forth. Besides, an Fe-Mn system, an Fe-Cr-Ni system, a U-Mo system, an Mn-Cu system, an Au-Cd system, etc. are usable.
The following table lists, for example, the compositions (weight %) and characteristics of Cu-Al-Ni alloy and the Ni-Ti alloy. Since each of these alloys can memorize the final shape at temperatures below the M.sub.f point and the final shape at temperatures above the F.sub.f point, it undergoes the cycles of the final shapes when subjected to these temperature cycles. It may accordingly be subjected to the shape memory so that a male contact and female contact may be in contact and electric conduction with each other in desired parts in a service temperature condition.
TABLE __________________________________________________________________________ Characteristics/ Compositions Cu - 14.0% Al - 4.0% Ni Ni - 44.3% Ti __________________________________________________________________________ Transformation temperature (.degree.C.) M.sub.s -124 -23 M.sub.f -140 -41 A.sub.s -117 -12 A.sub.f -71 3 Electric resistance 11 70 (.mu..OMEGA. .multidot. cm) Rupture strength 40 60 (kg/mm.sup.2) __________________________________________________________________________ ##STR1##
The female contact of the present invention is a flat thin film, with the thickness of the thin film being preferably 100.mu.m or less.
In the female contact of the present invention, the part forming the hole is preferably subjected to the shape memory so as to be capable of bending deformation in the direction in which the female contact comes into contact with the male contact, when changed to the parent phase transformation temperature of the shape memory alloy. Further, the connector of the present invention is preferably such that the male contact is inserted in the hole in a low temperature condition below the martensitic transformation temperature of the shape memory alloy, whereupon the connector has its temperature raised to the parent phase transformation temperature of the alloy so as to be returned into the original shape memorized. Since the male contact is inserted under the soft martensite state of the female contact, the insertion is permitted by a low insertion force, while during the service, the female contactor returns into the original state to afford a rigid connection.
In the present invention, preferably the part of the female contact, forming the hole, is subjected to the shape memory so as to form a space larger than the occupying space of the male contact in the contact part in the temperature condition lower than the martensitic transformation temperature of the shape memory alloy, the male contact being inserted in that state, whereupon the female contact has its temperature raised to above the parent phase transformation temperature of the alloy so as to return into its original shape. Since the male contact is inserted with the hole of the female contact expanded, the insertion is permitted by the zero insertion force, while, during the service of the connector, the contacts are rigidly connected as described above.
The hole portion of the female contact in the present invention is provided, in a portion adapted to contact with the male contact, with a slit or opening which is narrower than a space to be occupied by the male contact or with a slit which communicates with the hole portion. That is, a slit has a substantially H shape, with at least two slits being formed at equal intervals in the central part of the female contact, or that two or more slits are provided at the center of the circle. Further, it is favorable that the hole part is smaller than the occupying space of the male contact in the male contact area with this male contact. Likewise to the foregoing, the male contact is inserted into the female contact at a temperature below the martensitic transformation temperature, whereupon the female contact has its temperature raised to above the parent phase transformation temperature in the service temperature condition, to thereby afford the rigid connection.
Further, insulating substrates are arranged on the top face and bottom face of the female contact and are fastened to each other. With this connector, increase in the number of pins can be realized at a higher density, and miniaturization is also possible. Although the number of pins is 100-200 in LSI package for the present-day computer, it is anticipated to become 1000-2000 for a substrate of 10 cm square in the future. The present invention can cope with even such a number of pins. Further, according to the present invention, female contacts of a shape memory alloy can be disposed on the upper and lower surfaces of an insulating substrate similarly to the foregoing. When the female contact is disposed on one surface of the insulating substrate, the male contact is disposed on the opposite surface. The female contacts, or the female contact and male contact are electrically connected to each other.
As the insulating substrate, a multi-layer print-wired substrate or printed circuit board is used. In correspondence with the holes for inserting the male contacts, the female contacts of the shape memory alloy according to the present invention can be disposed in electrical connection.
The female contact of the present invention can be fabricated of only a shape memory alloy in the form of a thin film. Further it can be fabricated of a composite member in which thin metal film are deposited and adhered and in which at least one of the thin metal films is made of a shape memory alloy.
It is very difficult to plastically work a bulky shape memory alloy into a thin film. In contrast, the thin film, having a thickness of not greater than 0.1mm, can be formed by an evaporation method on a metal substrate or by pouring the molten metal on the peripheral surface of a rapidly rotating roll, for quenching and solidification. When the molten metal is poured on the mirror-finished surface of a roll having a thermal conductivity of at least 0.1 cal/cm.sec..degree. C. at the room temperature, the cooling rate of the molten metal until the solidification can be set at or above 10.sup.3 .degree. C./sec Thus, the alloy of very fine crystal grains is produced and can be plastically deformed, so that it can be worked even into a complicated shape. In order to form the thin film by a vapor process such as evaporation, the shape memory alloy needs to be formed in correspondence with holes which are provided in an insulating substrate. In this case, a metal foil is disposed on the insulating substrate in advance, and the shape memory alloy is deposited thereon. The alloy can be formed into a predetermined plane shape in correspondence with the holes of the insulating substrate, preferably by etching.
According to the present invention, a shape memory alloy is quenched from a vapor phase or liquid phase and is solidified on another metal member (substrate), whereby a composite member exhibiting the shape memory effect and having the characteristics of the substrate (or a different phase) can be produced along with the substrate or the different phase which has already been solidified on the substrate. As methods for quenching and solidification from the vapor phase or liquid phase, there are physical evaporation, chemical evaporation, molten metal quenching, flame spraying, etc. Concretely, the physical evaporation includes a general evaporation process, a sputtering process, an ion plating process, etc. The chemical evaporation is a solidifying process which is based on a chemical reaction in a gaseous state. Additionally, in the molten metal quenching method a metal alloy, in its molten state, is poured onto a substrate so as to cool it by contact with the substrate, and it is generally known as a process for producing an amorphous alloy. In particular, single-roll and two-roll methods etc. are known for manufacturing a thin strip and a fine wire by pouring the molten metal onto the surface of the roll which rotates at a high speed. In a flame spraying method, alloy powder, in its molten state, is atomized and solidified on a substrate. According to any of these methods, the alloy layer solidified on the substrate attains a good adhesion with the substrate or another metal which has already solidified on the substrate. Further, the crystal grains of the layer are rendered very fine due to the quenching and solidification. Thus, the stress concentration on a grain boundary due to a deformation is moderated by the fineness of the crystal grains, and the ductility of the shape memory alloy, which has been somewhat less ductile due to the coarsening of crystal grains, can be improved. Further, when a material which is higher in ductility than the shape memory alloy is used as the substrate, the fragility of the shape memory alloy can be compensated. Besides, when a material having a proper elasticity is selected for the substrate and is compounded with the shape memory alloy, the resultant substrate can be utilized as a spring member, and it is possible to control a temperature, a force etc. or with which the shape memory effect appears.
Any of the shape memory alloys is a multi-element alloy, and is therefore inferior to a pure metal in conductivity. According to the present invention, however, the shape memory alloy can be compounded along with a substrate of high conductivity such as Cu, Al, Au or Ag, so that a shape memory compound member of favorable conductivity can be fabricated.
The present invention also relates to a packaging structure for a semiconductor device wherein a multi-layer print-wired substrate, on which the semiconductor device is mounted, is connected to a connector, and the connector is then mounted on a printed circuit board, with the connector being made of a shape memory alloy having a plurality of holes which are provided in correspondence with a plurality of male contacts disposed in the multi-layer print-wired substrate as described above.
In accordance with the present invention, a packaging structure for a semiconductor device is provided having a multi-layer print-wired substrate on which the semiconductor device is mounted, and a printed circuit board on which the substrate is mounted, with the printed circuit board being provided with a female contact made of a shape memory alloy having a plurality of holes which are provided in correspondence with a plurality of male contacts disposed in the multi-layer print-wired substrate. Additionally, the present invention provides a packaging structure for a semiconductor device having a multi-layer print-wired substrate on which the semiconductor device is mounted, and a printed circuit board on which the substrate is mounted, with a multi-layer print-wired substrate being provided with a female contact made of a shape memory alloy having a plurality of holes which are provided in correspondence with a plurality of male contacts disposed in the semiconductor device.
The female contact of the present invention provided in the connector, the printed circuit board or the multi-layer print-wired substrate can be joined with the male contacts electrically and mechanically securely without soldering.